Inhibition of Spontaneous Combustion in Low-Rank Coals

ABSTRACT

A method for treating coal to reduce spontaneous combustion by reducing an exothermic heat of adsorption after the coal has begun to dry and when the coal is subsequently exposed to a liquid water is described. A source of a fluid pressure of a diluted hydrocarbon mixture is provided. A hydrocarbon in the mixture is a hydrocarbon emulsion of mineral when the coal is subsequently exposed to a liquid water oil, fuel oil, asphalt, or coal tar emulsions. A volume of the diluted hydrocarbon mixture is applied to a stream of freshly-mined and undried coal to provide a water-proofing of the coal to prevent water uptake after exposure to precipitation or flooding during transport and storage of the coal. The treated coal is loaded into a bulk pile. A temperature change trend in the bulk pile is reversed wherein a temperature of the bulk pile trends towards an ambient temperature rather than trending to a temperature higher than the ambient temperature.

TECHNICAL FIELD

The invention relates to coal mining as well as transport and storage ofcoal, and more particularly, the invention relates to a method fortreating coal to reduce or prevent spontaneous combustion by reducingthe exothermic heat of adsorption after the coal has begun to dry andwhen the coal is subsequently exposed to liquid water.

BACKGROUND OF THE INVENTION

The spontaneous combustion of coal is a serious problem for utilities,both during transport and on-site handling. In addition to the loss offuel, attempting to handle ignited coal can initiate combustion eventsthat lead to the detonation of coal dust, forcing utilities to shut downfor weeks to months with losses from electricity generating revenue andadditional costs from construction to replace the destroyedinfrastructure.

The problem of spontaneous combustion has been recognized for manydecades. U.S. Pat. No. 2,184,621 (Marmaduke, 1938) cites coal's abilityto spontaneously ignite and proposes a remedy of encapsulating the coalin a plasticized wax treatment. More recently, the issue has beenaddressed by encapsulating the coal in layers of silicon dioxide (Kindiget al., U.S. Pat. No. 3,961,914), high molecular weight polyethyleneglycol (Burns, U.S. Pat. No. 4,331,445), latex (Matthews, U.S. Pat. No.4,421,520), pre-oxidizing the coal with a chemical oxidizer (Rogers etal., U.S. Pat. No. 4,759,772), or, more recently, treating the coal witha polymeric cationic surfactant (Roe, U.S. Pat. No. 5,576,056).

In addition to attempting to treat the coal surface, the problem ofspontaneous combustion has been approached by attempting to inert thecoal surface with carbon dioxide (Smith, U.S. Pat. No. 4,199,325), bydrying and partially oxidizing then hydrating the coal (Seitzer, U.S.Pat. No. 3,723,079), by drying the coal and briquetting it (Kubota etal., U.S. Pat. No. 4,645,513), by drying and then sealing the coal witha hydrocarbon oil or wax (Johnson, U.S. Pat. No. 3,985,517; Bixel etal., U.S. Pat. No. 4,783,199 and 4,828,576), by pulverizing and dryingthe coal while removing the ash and then binding the particles with coaltar (Knudson et al., U.S. Pat. No. 5,162,050), and by pulverizing,drying, and sealing the coal particles with mineral oil (Dunlop et al.,U.S. Pat. No. 6,162,265) or a mixture of oil and molasses (Rahm et al.,U.S. Pat. No. 6,086,647).

Finally, two patents have taught that management of the coal pile itselfto decrease air penetration reduce the likelihood of spontaneouscombustion (Behringer, U.S. Pat. No. 4,472,102 and Reeves et al., U.S.Pat. No. 6,231,627).

The conventional wisdom is that spontaneous combustion of low-rank coalis an oxidation process. Indeed, at higher temperatures it is exactlythat. However, at or near room temperature the rate of oxidation of coalis very slow. Interestingly, spontaneous combustion of coal piles occursmost frequently during wet weather, especially wet weather following adry spell. In the 1990's, significant research was carried out on therole water played in the initial heating of coal. A thorough review waspublished in 2001: “The Influence of Moisture on the SpontaneousCombustion of Coal” Christopher Blazek, Benetech Report. The reporthighlighted several additional sources of heat that can occur in a coalpile. Among them, the heat of condensation and the heat of adsorptionprovide significant thermal energy to the coal particle. Of course, thereverse of these processes would provide an equal amount of thermalcooling, provided the particle remains unchanged. In the case ofsub-bituminous and lignite coals this is not the case. Sub-bituminouscoal can contain up to 30% moisture incorporated into the coal body. Assuch, it is an integral structural component of the coal particle.Drying the coal, whether through natural or artificial processes, causesthe coal's structure to break down. It is this phenomena that accountsfor the notorious dustiness of Powder River Basin (PRB) and othersub-bituminous coals. In the process of breaking down, an irreversiblechange occurs to the coal. It fragments. As it fragments, its surfacearea increases.

To illustrate this consider a cube of freshly-mined sub-bituminous coal.Its initial surface area is 6 units, that is, it is a cube of unitlength, width, and depth. As it dries it loses water and eventuallyfragments. Let us say that it has now split evenly into eight pieces,that is, it is now eight cubes of half unit length, width, and depth,and each will now have a surface area of 1.5 units, for a total surfacearea of 12 units. Its water content has dropped to 15%. Its mass is now0.85 kg. Suppose now that the 150 grams of water is returned to thecoal. The endothermic heat of evaporation and the exothermic heat ofcondensation will offset each other. However, the heat of desorption andthe heat of adsorption are proportional to the surface area of the coaland that has changed. The heat of adsorption will now be approximatelytwice as great as the heat of desorption. The net effect will be heatingof the coal particles. This low-temperature heating of the coal via theheat of adsorption, also called the heat of wetting or the heat ofimmersion, can heat the coal from a temperature where the rate ofoxidation is too low to support a self-sustaining reaction to atemperature where oxidation can become self-sustaining. In other words,this heat of adsorption can act as the match to light a coal pile fire.

It is therefore important to understand the previous work onwaterproofing treatments for coal. Notably, in addition to the teachingsin the Johnson, Bixel, Knudson, and Dunlop patents that were used towaterproof dried, pulverized coal, sodium silicate and sugar were usedto produce hard waterproof briquettes of bituminous coal powder astaught by Miller (Miller, U.S. Pat. No. 1,670,865), a mixture ofresidual fuel oil (decant oil) and asphalt was applied to lignite, andspecifically dried lignite (Anderson, U.S. Pat. No. 4,201,657), in atwo-step process as-mined coal is treated with a pile-sealing coating ofwetting agent and asphalt (Shaw et al., U.S. Pat. No. 4,264,333), driedcoal was treated with petroleum resin cut with a variety of oils for useas a dust control formula (Wajer et al., U.S. Pat. No. 5,192,337), andfinally a pulverized coal slurry was treated with mineral oil emulsionsto agglomerate and reduce dusting (Roe, U.S. Pat. No. 5,256,169).

To summarize the prior art, spontaneous combustion inhibition forun-dried coal was claimed for treatments composed of a variety of oil,coal tar, latex, high molecular weight polyethylene glycols, and asphaltcompositions applied neat at a minimum rate of 0.5 gallons (about 4pounds) per ton. The literature draws a sharp distinction betweenfresh-mined coal and the more reactive dried low-grade coal.Comparatively little attention has been given to preventing spontaneouscombustion during handling and transport of fresh-mined coal. Inaddition, coal producers are sensitive to the price of coal treatmentsand even half a gallon of pure mineral oil, fuel oil, or coal tar perton would represent a significant economic consideration to a mine thatproduces millions of tons of coal per year.

The present invention is provided to solve the problems discussed aboveand other problems, and to provide advantages and aspects not providedby prior methods of inhibiting the spontaneous combustion of low-rankcoals. A full discussion of the features and advantages of the presentinvention is deferred to the following detailed description, whichproceeds with reference to the accompanying drawings.

SUMMARY OF THE INVENTION

A first aspect of the present invention is directed to a method fortreating coal to reduce spontaneous combustion by reducing an exothermicheat of adsorption after the coal has begun to dry and when the coal issubsequently exposed to a liquid water. The method comprises the stepsof: providing a source of a fluid pressure of a hydrocarbon; andapplying the hydrocarbon to a stream of coal.

This aspect of the present invention may include one or more of thefollowing features, alone or in any reasonable combination. Thehydrocarbon may be a hydrocarbon emulsion. A low-level amount of thehydrocarbon emulsion may be applied to the coal as a percentage of aweight of the coal. The hydrocarbon emulsion may be selected from thegroup consisting of: mineral oil, fuel oil, asphalt, and coal taremulsions. The coal may be fresh-mined and un-dried. The hydrocarbonemulsion may reduce self-heating of the coal caused by exothermic heatof absorption.

A second aspect of the present invention is directed to a method fortreating coal to reduce spontaneous combustion by reducing an exothermicheat of adsorption after the coal has begun to dry and when the coal issubsequently exposed to a liquid water. The method comprises the stepsof: providing a source of a fluid pressure of a silicone; and applyingthe silicone to a stream of coal.

This aspect of the present invention may include one or more of thefollowing features, alone or in any reasonable combination. The siliconemay be a silicone emulsion. A low-level amount of the silicone emulsionmay be applied to the coal as a percentage of a weight of the coal.

A third aspect of the present invention is directed to a method fortreating coal to reduce spontaneous combustion by reducing an exothermicheat of adsorption after the coal has begun to dry and when the coal issubsequently exposed to a liquid water. The method comprises the stepsof: providing a source of a fluid pressure of a silane; and applying thesilane to a stream of coal.

This aspect of the present invention may include one or more of thefollowing features, alone or in any reasonable combination. A low-levelamount of the silane may be applied to the coal as a percentage of aweight of the coal.

A fourth aspect of the present invention is directed to a method fortreating coal to reduce spontaneous combustion by reducing an exothermicheat of adsorption after the coal has begun to dry and when the coal issubsequently exposed to a liquid water comprising the step ofwaterproofing a freshly-mined coal to prevent water uptake afterexposure to precipitation or flooding during transport and storage ofthe freshly-mined coal.

This aspect of the present invention may include one or more of thefollowing features, alone or in any reasonable combination. The methodmay further comprise the steps of: providing a source of a fluidpressure of a hydrocarbon; and applying the hydrocarbon to a stream offreshly-mined and undried coal. The applying step may includeapplication of a low-level amount of the hydrocarbon as a percentage ofthe weight of the coal. The hydrocarbon may be a hydrocarbon emulsion.The low-level amount of the hydrocarbon emulsion may be not more than 2lb (0.9 kg) per ton of the coal prior to dilution with water. Thehydrocarbon emulsion may be diluted in liquid water prior to theapplying step. A diluted mixture of the hydrocarbon emulsion and theliquid water may contain less than 80 parts liquid water. The mixturemay contain up to 100 parts water. The diluted mixture may containbetween 19 and 79 parts liquid water. An application rate of the dilutedmixture may be 2.5 to 10 gallons of diluted mixture per ton offreshly-mined and undried coal. An application rate of the dilutedmixture may be as low as 0.5 gallons of diluted mixture per ton offreshly-mined and undried coal. The applying step may be accomplishedusing a pump and spray manifold on either side of the stream offreshly-mined and undried coal. The hydrocarbon emulsion may be selectedfrom the group consisting of: mineral oil, fuel oil, asphalt, and coaltar emulsions. The method may further comprise the step of: developing awater repellency of the freshly-mined and undried coal by allowing thecoal to dry under ambient conditions. The method may further comprisethe steps of: loading the freshly-mined and undried coal into a bulkpile subsequent to the applying step; and reversing a temperature changetrend in the bulk pile wherein a temperature of the bulk pile trendstowards an ambient temperature rather than trending to a temperaturehigher than the ambient temperature.

A fifth aspect of the present invention is directed to a method fortreating coal to reduce spontaneous combustion by reducing an exothermicheat of adsorption after the coal has begun to dry and when the coal issubsequently exposed to a liquid water. The method comprises the stepsof: providing a source of a fluid pressure of a diluted hydrocarbonmixture wherein a hydrocarbon in the diluted hydrocarbon mixture is ahydrocarbon emulsion chosen from the group consisting of mineral oil,fuel oil, asphalt, and coal tar emulsions, and the hydrocarbon emulsion;applying a volume of the diluted hydrocarbon mixture to a stream offreshly-mined and undried coal to provide a waterproofing of thefreshly-mined and undried coal to prevent water uptake after exposure toprecipitation or flooding during transport and storage of thefreshly-mined coal; loading the freshly-mined and undried coal into abulk pile subsequent to the applying step; and reversing a temperaturechange trend in the bulk pile wherein a temperature of the bulk piletrends towards an ambient temperature rather than trending to atemperature higher than the ambient temperature.

This aspect of the present invention may include one or more of thefollowing features, alone or in any reasonable combination. Thehydrocarbon may be diluted with water such that the diluted hydrocarbonmixture contains between 19 and 79 parts liquid water by volume prior tothe applying step. An application rate of the diluted hydrocarbonmixture may be 2.5 to 10 gallons of diluted hydrocarbon mixture per tonof freshly-mined and undried coal. A low-level amount of the hydrocarbonmay be applied to the freshly-mined and undried coal in an amount nogreater than 1 lb (0.45 kg) per ton of the freshly-mined and undriedcoal.

A sixth aspect of the present invention is directed to a method ofimproving the net energy content of a fuel exposed to rain or flooding.This method comprises the step of: waterproofing a fuel to prevent wateruptake after exposure to precipitation or flooding during transport andstorage of the fuel.

This aspect of the present invention may include one or more of thefollowing features, alone or in any reasonable combination. The methodmay further comprise the steps of: providing a source of a fluid of awaterproofing agent, wherein the waterproofing agent is selected fromthe group consisting of a hydrocarbon, a hydrocarbon emulsion, asilicone, and a silane; and applying the waterproofing agent to thefuel. A low-level amount of the waterproofing agent may be applied tothe fuel as a percentage of a weight of the fuel. The hydrocarbonemulsion may be selected from the group consisting of: mineral oil, fueloil, asphalt, and coal tar emulsions. The hydrocarbon emulsion mayreduce self-heating of the coal caused by exothermic heat of absorption.The fuel may be a coal. The coal may be freshly-mined. The coal may beundried. The fuel may be low-rank, sub-bituminous or lignite coal.

Other features and advantages of the invention will be apparent from thefollowing specification taken in conjunction with the followingdrawings.

BRIEF DESCRIPTION OF THE DRAWINGS

To understand the present invention, it will now be described by way ofexample, with reference to the accompanying drawings in which:

FIG. 1 is a flowchart of an aspect of the present invention;

FIG. 2 is a flowchart of an aspect of the present invention;

FIG. 3 is a flowchart of an aspect of the present invention; and

FIG. 4 is a flowchart of an aspect of the present invention.

DETAILED DESCRIPTION

While this invention is susceptible of embodiments in many differentforms, there is shown in the drawings and will herein be described indetail preferred embodiments of the invention with the understandingthat the present disclosure is to be considered as an exemplification ofthe principles of the invention and is not intended to limit the broadaspect of the invention to the embodiments illustrated.

Our invention is directed to a method for treating to reduce oreliminate the likelihood spontaneous combustion. Treatment can occur anytime before the coal is subjected to spontaneous combustion; however, ina preferred method fresh-mined and specifically un-dried coal is treatedto reduce or prevent spontaneous combustion by reducing or preventingthe exothermic heat of adsorption after the coal has begun to dry andwhen the coal is subsequently exposed to liquid water. This isaccomplished by treating the coal with a waterproofing agent such thatwhen exposed to water the water runs off and fails to adsorb onto orinto the coal particles, thus waterproofing the coal. Freshly-mined inthis context is coal that has not substantially lost its initial watercontent.

The composition generally requires a water-proofing material selectedfrom polysiloxanes, silazanes, mineral oil, fuel oil, coal tar, asphalt,petrolatum, vegetable-derived oils, animal-derived oils, creosotes, talloil pitch, petroleum pitch, petroleum resins, and emulsions thereof.Other water-proofing compositions will be apparent to those skilled inthe art. The effective application rate of these materials isconsiderably below the levels reported in previous patents. For example,in one embodiment a mineral oil emulsion was applied at 0.425 lbs (0.05gallons) of mineral oil per ton of coal and gave near-completewater-proofing of the coal. In another case, a coal tar emulsion wasapplied at about 0.8 pounds per ton of coal and gave coal that shedwater and showed no tendency to self-heat. The inventors contemplatethat less than 2 lbs of an emulsion per ton of coal as described hereincan be used to treat a bulk load or pile of coal to arrive at suitablereduction in spontaneous combustion of the coal under the circumstancesor chemical processes described herein. And, in an example describedherein, less than 1 lb per ton of the coal tar itself can be used totreat the coal.

The waterproofing compositions of interest are, where possible, aqueousemulsions of the above-mentioned water-proofing materials. This is notto say that application of the pure waterproofing product will not work.It is simply that emulsions have several advantages over the purematerial. First, being able to be diluted in water allows effectivecoating of the coal surface at a much lower application rate. Second,aqueous emulsions are not combustible. Combustibility is an importantconsideration at any mine of coal-handling facility as coal fires are ahazard and storing a combustible material on site is not desirable.

It should be noted that water reduction in fuel subjected to rain orflooding can also have significant benefits. Every kilogram of waterthat goes into a boiler on the fuel costs about 2.3 megajoules inunrecoverable thermal energy. Thus, a 3% reduction in moisture on a 19.5MJ/kg (8400 BTU/lb) fuel will result in a thermal energy gain of about138 MJ/MT. Assuming a total plant thermal to electrical energyconversion efficiency of about 35%, that would be about another 13kWh/MT of fuel. Thus, the teaching of this invention may be applied to amethod of improving the net energy content of a fuel exposed to rain orflooding. The fuel is preferably a low-rank, sub-bituminous or lignitecoal.

These emulsions 10 are diluted with water and applied as a spray 12 to acoal stream 14, usually at a transfer point where both sides of the coalstream can be treated for thorough coverage. Typically the emulsion isdiluted 1 part emulsion to 19 parts water to 1 part emulsion to 79 partsmoisture and a diluted mixture is then applied at a rate of twenty toeighty pounds (2.5 to 10 gallons) per ton of coal. The application isgenerally accomplished using a pump and spray manifolds on either sideof the coal stream. The application of the waterproofing agentsdisclosed herein can also be applied as a foam.

The coal is then allowed to dry, usually on a coal pile, barge, or in arailcar, developing water repellency as it does so. Generally, dependingon ambient temperature, solar insolation, and relative humidity, thiscan take as little as an hour or as long as several hours.

The effect of waterproofing is long-lasting. In experiments designed todetermine the longevity of the treatment, water-shedding wasundiminished after twenty-eight days.

Example 1 Heat of Wetting

To examine the heat of water adsorption and determine whether a surfacetreatment could affect this, freshly-produced coal particles weresieved, and a fraction between 18 and 60 mesh was isolated. The coal wastreated with a variety of agents and then dried at 40° C. overnight, or,in some cases, for several days. A one liter vacuum dewar flaskcalorimeter containing a magnetic stir bar, thermocouple, and 100 gramsof deionized water was assembled and allowed to come to equilibrium. Thethermocouple was attached to a data recorder sampling at one data pointper second. Twenty grams of the treated coal was then added to thecalorimeter with stirring and the thermocouple was used to vigorouslymix the coal into the water insuring complete wetting over a period offive to ten seconds. The temperature of the water and coal mixture wasmonitored and after between five and twenty minutes the temperature wasextrapolated back to the point at which the coal was added. The heat ofadsorption was then calculated and Table 1 was generated.

TABLE 1 Heat of Adsorption for Treated Coal Average Heat of Treatment(scaled for adsorption, sub-2″ coal) J/g Test 1 Test 2 Test 3 Tap water44.6 J/g 52.50878 43.99085 44.87238 Mineral oil emulsion 46.0 J/g56.59566 40.03123 41.28364 @ 196 g emulsion/MT Silicone emulsion @ 45.4J/g 51.10731 43.45505 41.69884 72.2 g emulsion/MT Latex emulsion @ 46.9J/g 51.04161 44.54425 45.12869 87.0 g emulsion/MT Mineral oil emulsion45.5 J/g 46.74927 44.75394 44.89994 @ 392 g emulsion/MT Siliconeemulsion @ 43.6 J/g 45.57953 42.3645 42.89594 144.4 g emulsion/MT Latexemulsion@ 41.6 J/g 41.8583 42.69309 40.19634 174 g emulsion/MT

The treatment rate listed was scaled to account for the particle sizedifference between 18-60 mesh and sub-5.08 cm fresh coal. In otherwords, because of the difference in surface area the 18-60 mesh, coalwas treated at a higher rate to achieve the same treatment per surfacearea as would be the case for treating sub-5.08 cm coal.

As can be seen, the treatment of coal in this experiment had no effect(P<0.05) on the heat of adsorption when it was forced to wet.

Example 2 Perk Tests

Approximately 30 kg of <5.08 cm coal was treated with the indicatedtreatment (see Table 2), divided into three approximately equal portionsand allowed to dry for four days. All treatments added a total ofapproximately 4% by weight of water solution to the coal. The portionswere divided in four and each portion in four parts was loaded into aseparate tared 15.25 cm diameter translucent schedule 40 PVC tube thatwas closed at one end with a cotton cloth. The combined sample plus tubewas re-weighed and the weight recorded. The coal filled the tube to adepth of 61 to 66 cm. Approximately 8.8 kg of water were poured into thetop of the tube and the time it took to run out was recorded. The tubewas then re-weighed and the coal was poured out of the tube andexamined. In spite of the large amount of water that was poured throughthe coal sample, the majority of the mineral oil emulsion treated coalwas still dry. The experiment was repeated five days later, that is,after the coal had been treated and allowed to stand for four days andthen tested and allowed to stand for another five days the same sampleswere re-tested. The tests were repeated a week later on the sixteen dayold coal. The treatment and observations are summarized in Table 2.

TABLE 2 Perk Tests on <5.08 cm Coal Water on Percent Water on PercentWater on Percent the coal, Drain time, dry coal, the coal, Drain time,dry coal, the coal, Drain time, dry coal, 4 day 4 day 4 day 9 day 9 day9 day 16 day 16 day 16 day Treatment old coal old coal old coal old coalold coal old coal old coal old coal old coal Water 1.7 kg 77.56 min 1%2.6 kg columns 0% 1.7 kg columns 0% plugged plugged Oil 0.7 kg 15.00 min90%  0.9 kg 7.37 min 96%    1 kg 5.833 min 93%  emulsion @ 351 g/MT SBRLatex 2.1 kg 71.47 min 2% N/A N/A N/A N/A N/A N/A emulsion @ 252 g/MT

As can be seen, small amounts of mineral oil emulsion have a profoundimpact on the wetting of treated coal, rendering the coal effectivelywaterproof even after protracted periods and even after exposure tosignificant quantities of liquid water. Surprisingly, the SBR Latextreated coal was not rendered waterproof.

It was also noted after 9 and 16 days that the treated aged coal in thetest of this example had a much lower water content. In each case thewater content was measured on an Ohaus moisture balance before eachsample was loaded into the column. Thus the water reported herein waswater that was original to the coal plus water that it had picked upduring the previous perk tests on days 4 and 9 respectively. Table 3illustrates these observations:

TABLE 3 Moisture Content of Coal Day 16 coal moisture Day 9 coalmoisture content content (prior Treatment (prior to perk test) to perktest) Water 30.68% 42.81% Oil emulsion @ 351 g/MT 24.51% 21.79%

We attribute this to the mineral oil inhibiting re-uptake of liquidwater, a logical consequence of waterproofing and then adding roughly8.8 kg (89% by weight) water to the coal during the perk test. Lowerwater content is desirable in coal as that results in a higher energycontent per unit mass.

Example 3 Large-Scale Test

Approximately 75,000 short tons of freshly mined Powder River Basin(PRB) coal were treated at an average rate of 0.8 lbs of coal tar perton (330 grams per metric ton) using a coal tar emulsion. During theapplication, and subsequent to it, the coal was subjected to 43-63 cm ofrain as it was treated then transported via open barge to an oceanfreighter. On loading the average coal temperature was 33° C. Duringtransport across the Atlantic Ocean, the ship's captain pumped off 700short tons of water from the hold, indicating that the treated coal wasshedding surface water. This was an unusual occurrence—generally coalwill not shed water during transport. Upon unloading the average coaltemperature was 31° C. It was clear that in addition to shedding waterthe coal had not experienced self-heating. The coal was stacked out atthe receiving dock and the temperature was monitored for five days:

TABLE 4 Temperature of Stacked-Out Treated Coal Treated coal Comparisonambient temperature temperature Day 1 27.9° C.  6.7° C. Day 2 22.0° C. 6.4° C. Day 3 17.7° C. 13.1° C. Day 4 18.0° C. 16.9° C. Day 5 18.0° C.16.7° C.

In contrast to this, another approximately equal amount of coal with thesame transportation history but not treated with the coal tar emulsionexperienced significant self-heating after being stacked out.

TABLE 5 Untreated Coal after Stack-Out Untreated Untreated CoalComparison ambient temperature temperature Day 1 20.5° C. 10.3° C. Day 222.2° C. 12.5° C. Day 3 25.6° C. 13.6° C. Day 4 29.9° C. 16.9° C.

From the above data it is clear that the addition of a waterproofingagent to freshly mined low-rank coal will interfere with one of thebasic mechanisms of low temperature self-heating for that coal. Acomparison of the data in Table 4 to the data in Table 5 shows that atemperature change trend in a bulk pile of the coal can be reversedusing the treatment of the present invention. A temperature of the bulkpile of treated coal in Table 4 trends towards an ambient temperaturerather than trending to a temperature higher than the ambienttemperature as experienced by the untreated bulk pile of coal datapresented in Table 5.

While the specific embodiments have been illustrated and described,numerous modifications come to mind without significantly departing fromthe spirit of the invention, and the scope of protection is only limitedby the scope of the accompanying Claims.

1. A method for treating coal to reduce spontaneous combustion byreducing an exothermic heat of adsorption after the coal has begun todry and when the coal is subsequently exposed to a liquid watercomprising the steps of: providing a source of a fluid pressure of ahydrocarbon; and applying the hydrocarbon to a stream of coal.
 2. Themethod of claim 1 wherein the hydrocarbon is a hydrocarbon emulsion. 3.The method of claim 2 wherein a low-level amount of the hydrocarbonemulsion is applied to the coal as a percentage of a weight of the coal.4. The method of claim 3 wherein the hydrocarbon emulsion is selectedfrom the group consisting of: mineral oil, fuel oil, asphalt, and coaltar emulsions.
 5. The method of claim 4 wherein the coal isfreshly-mined and un-dried.
 6. The method of claim 5 wherein thehydrocarbon emulsion reduces self-heating of the coal caused byexothermic heat of absorption.
 7. A method for treating coal to reducespontaneous combustion by reducing an exothermic heat of adsorptionafter the coal has begun to dry and when the coal is subsequentlyexposed to a liquid water comprising the steps of: providing a source ofa fluid pressure of a silicone; and applying the silicone to a stream ofcoal.
 8. The method of claim 7 wherein the silicone is a siliconeemulsion.
 9. The method of claim 8 wherein a low-level amount of thesilicone emulsion is applied to the coal as a percentage of a weight ofthe coal.
 10. A method for treating coal to reduce spontaneouscombustion by reducing an exothermic heat of adsorption after the coalhas begun to dry and when the coal is subsequently exposed to a liquidwater comprising the steps of: providing a source of a fluid pressure ofa silane; and applying the silane to a stream of coal.
 11. The method ofclaim 10 wherein a low-level amount of the silane is applied to the coalas a percentage of a weight of the coal.
 12. A method for treating coalto reduce spontaneous combustion by reducing an exothermic heat ofadsorption after the coal has begun to dry and when the coal issubsequently exposed to a liquid water comprising the step ofwaterproofing a freshly-mined coal to prevent water uptake afterexposure to precipitation or flooding during transport and storage ofthe freshly-mined coal.
 13. The method of claim 12 further comprisingthe steps of: providing a source of a fluid pressure of a hydrocarbon;and applying the hydrocarbon to a stream of freshly-mined and undriedcoal.
 14. The method of claim 13 wherein the applying step includesapplication of a low-level amount of the hydrocarbon as a percentage ofthe weight of the coal.
 15. The method of claim 14 wherein thehydrocarbon is a hydrocarbon emulsion.
 16. The method of claim 15wherein the low-level amount of the hydrocarbon emulsion is not morethan 2 lb (0.9 kg) per ton of the coal.
 17. The method of claim 16wherein the hydrocarbon emulsion is diluted in liquid water prior to theapplying step.
 18. The method of claim 17 wherein a diluted mixture ofthe hydrocarbon emulsion and the liquid water contains less than 80parts liquid water.
 19. The method of claim 18 wherein the dilutedmixture contains between 19 and 79 parts liquid water.
 20. The method ofclaim 19 wherein an application rate of the diluted mixture is 2.5 to 10gallons of diluted mixture per ton of freshly-mined and undried coal.21. The method of claim 20 wherein the hydrocarbon emulsion is selectedfrom the group consisting of: mineral oil, fuel oil, asphalt, and coaltar emulsions.
 22. The method of claim 21 further comprising the stepof: developing a water repellency of the freshly-mined and undried coalby allowing the coal to dry under ambient conditions.
 23. The method ofclaim 21 further comprising the steps of: loading the freshly-mined andundried coal into a bulk pile subsequent to the applying step; andreversing a temperature change trend in the bulk pile wherein atemperature of the bulk pile trends towards an ambient temperaturerather than trending to a temperature higher than the ambienttemperature. 24.-36. (canceled)